Which of the following countries had the longest civil war angola liberia democratic republic of congo ethiopia

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

Most of earths fresh surface water is found in

Which barrier to economic development is shown in the following examples?